Ocular lenses are worn by many people to correct vision problems. Vision problems are caused by aberrations of the light rays entering the eyes. These include low order aberrations, such as myopia, hyperopia, and astigmatism, and higher order aberrations, such as spherical, coma, trefoil, and chromatic aberrations. Because the distortion introduced by aberrations into an optical system significantly degrades the quality of the images on the image plane of such system, there are advantages to the reduction of those aberrations.
Ocular lenses are typically made by writing prescriptions to lens blanks. This is accomplished by altering the topography of the surface of a lens blank.
Recently, attention has been given to methods of writing a low order lens using a patient's measured wavefront information. Currently, several techniques can be utilized to determine the optimum low order refraction from the high order, including: the Gaussian Least Squares Fit, point spread optimization, and neural network analysis. Some of these techniques may be employed to not only derive the best low order prescription from the high order values, but may also be used to “fit” an optimum wavefront across an entire spectacle lens based on the patient's measured wavefront.
Using one or more of these fitting techniques may yield a better refraction than conventional subjective refractions in the center zone, but consideration must be given to off-axis gaze angles. In particular, one considerable disadvantage of traditional lens manufacturing is that that many people experience distortion when looking off-center outside the central region, commonly called “swim”.
Accordingly, there is a need for a method of determining a wavefront for a patient's spectacle based on the patient's measured wavefront, in such a way to reduce distortion when the patient looks off center outside the central region.